1. Field of the Invention
The present invention pertains, in general, to an organometallic precursor for forming a very pure metal film or pattern and a method of forming the metal film or pattern using the same. More particularly, the present invention relates to an organometallic precursor containing a hydrazine compound coordinating with a central metal thereof, and a method of forming a metal film or pattern using the same. Further, the present invention relates to a composition containing an organometallic compound and a hydrazine compound, and a method of forming a metal film or pattern using the same.
2. Description of the Related Art
A metal pattern to be formed on a substrate continues to get smaller in accordance with the recent trend of an increase in the degree of integration and a decrease in the size of electronic devices such as integrated circuits (IC) and Liquid crystalline displays. Usually, the metal pattern is formed on the substrate through a photolithography process using a photoresist. The photolithography process generally includes a) forming a metal layer on a substrate via a chemical vapor deposition process (CVD process), a plasma deposition process, or an electrical plating process, b) coating a photoresist on the metal layer, c) exposing the photoresist to UV-radiation under a photomask and d) developing photoresist layer to obtain a patterned photoresist layer, and e) etching the metal layer under the pattern of photoresist with, for example, a reactive ion-etching process to form a metal pattern on the substrate.
However, since the photolithography process involves many complicated steps and requires the use of a large amount of fine chemicals such as expensive photoresist compositions and etchants, it is undesirable in terms of cost and environmental protection. In the photolithography process, there are many steps, such as depositing and etching that should be conducted at a high temperature and/or high pressure, and thus, operational costs are also high. Also, metal vapor diffusion possibly occurring in the process when high temperature are employed often brings about deteriorations in the performance of an electronic device and defects in the device. Especially, for a flexible display or a TFT-LCD to achieve a high quality picture and a large-scaled screen, a technology is urgently required to be developed that can form a gate dielectric layer of high quality and a source/drain electrode region with low resistance. Thus, many studies have been made on the formation of a metal film or pattern through a simple procedure at a relatively low temperature.
As an alternative technology that can substitute for photolithography process, soft-lithography and ink-jet printing are attracting attention because they can form a fine pattern on a substrate with relatively simplified procedures and low operation costs. However, these two processes still have the problems that a film or a pattern must be heat-treated, or additionally oxidized or reduced at a high temperature in order for the film or pattern thus obtained to have lower resistivity. Therefore, when considering the materials currently used for the substrate, there remains a need to develop an ink which can form a metal pattern with high durability and high conductivity at a high resolution via a more simplified process requiring a low temperature.
IEEE Transactions on components Hybrids and Manufacturing Technology 12(4), 1987 (“Liquid ink-jet printing with MOD inks for hybrid microcircuits”, Teng, K. F. and Vest, R. W.) discloses organometallic compounds that can be thermally decomposed at low temperatures and converted into metals or metal oxides, so called metallo-organic decomposition compounds (MOD compounds). Also, U.S. Pat. No. 5,882,722 discloses a technology of forming a metal film or pattern using the MOD compounds. However, this technology is disadvantageous because of the problem that the metal film or pattern thus formed is apt to be molten before thermal-decomposition so it is very difficult to secure the required thickness of the metal film or pattern while obtaining a conductivity of the metal film or pattern that is high. To avoid this problem, use of a multi-coating layer has been proposed as an alternative, but it is not good because coating multi-layers entails not only many complicated steps but also high costs. U.S. Pat. No. 5,173,330 discloses a method using organo-metal precursors to form a metal thin film or nuclei that is normally used in an electrolytic plating process but this method is undesirable because of low conductivity of the obtained film or pattern. Further, U.S. Pat. Nos. 4,186,244 and 4,463,030 disclose a process of forming a metal film by using silver (Ag) powder and a surfactant wrapping the silver powder at a low temperature. However, this process is disadvantageous in that, after formation, the metal film should be exposed to a temperature of 600° C. or higher in order to remove the surfactant. If the metal film is not exposed to this high temperature, the specific resistivity of the metal film becomes undesirably increased because of organic materials remaining on the metal film.
Additionally, U.S. Pat. No. 6,036,889 discloses a process of forming a relatively highly conductive metal pattern with a specific resistivity of about 3.0 μΩcm−1 on a polymer substrate at the low temperatures of 350° C. or lower using a mixture of MOD compounds, metal flakes, and metal colloid. In this process, the MOD compounds play a role in lowering the required temperature for heat treatment, while aiding the coating of composition on the substrate, and the metal flakes promote the solidification of a precursor to prevent the MOD compounds from being melted before the formation of the metal pattern. This process overcomes the conventional problems by using a mixture of many compounds wherein one compound helps avoid the problems of other compounds so it can be possible to form the metal pattern with excellent properties. However, there is a limitation in improving the properties of the metal pattern because the fundamental problems in the prior art are not solved completely and the content of each compound is limited. Hence, it is impossible for this process to form a metal film or pattern with a high conductivity corresponding to a pure metal at a temperature of 250° C. or lower.
Therefore, there remains a need to develop a method of forming a metal film or pattern, wherein the film or pattern has high conductivity corresponding to that of a pure metal. Moreover, a simple procedure is desired that uses a relatively low temperature wherein the thickness of the metal film can be controlled successfully.
The present inventors have conducted extensive studies on this need and, as a result of the study, have developed a method of forming a highly conductive metal film or pattern through a simple procedure at a relatively low temperature, wherein, by treating i) an organometallic precursor compound containing as a ligand a specific compound with high reducing ability, or ii) a composition comprising the specific compound and an organometallic compound at a low temperature of 400° C. or lower, preferably 250° C. or lower, a central metal of the organometallic precursor compound or the composition is reduced with the decomposition of organic compounds. Through this method, a highly conductive metal film or pattern with specific resistivity of 2.5 to 3.0 μΩcm−1 can be formed.